Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/18/17

Area Forecast Discussion
National Weather Service Taunton MA
938 PM EST Sun Dec 17 2017 .SYNOPSIS... A weak wave of low pressure will bring a period of light snow overnight into Monday morning, which may linger into the afternoon across northeast Massachusetts. Temperatures will be milder on Tuesday ahead of a cold front, then turn blustery and colder Wednesday into Thursday but with dry weather prevailing. Low pressure will likely pass to our west Friday night and Saturday, probably bringing mainly rain and a period of rather mild temperatures along with some wind. A period of unsettled weather may return sometime Christmas Eve into Christmas, but timing and precipitation types are uncertain. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 935 PM update... Forecast on track. It will take several hours to moisten lower levels given very dry air in place. Expect light snow to move into western New Eng after midnight with any snowfall more spotty as it reaches eastern MA toward daybreak. Only minor temp drop overnight with increasing cloud cover. Previous discussion... Tonight into Monday morning... ***Light snow will likely impact the Monday morning commute*** Dry weather persists through late evening as mid level cloudiness continues to thicken. Temps will generally range from the teens to middle 20s through midnight. Increasing potential for light snow showers to develop during the overnight hours and move through southern New England during the morning commute. Low pressure over the Great Lakes will slowly begin to move towards the Northeast pushing the frontal system to our south northward as a warm front. Ahead of the front, isentropic lift within the WAA pattern will help provide just enough lift for precip to occur. Increasing moisture in the mid-levels will help saturate the snow growth region and with soundings keeping the profile below 0C anticipate snow showers. The lift does appear weak thus continued the mention of light snow showers late tonight and into the morning hours. One thing we will have to watch is the warm layer at 950mb. Both the EC and HRRR are in agreement of thermals which keeps this warm layer just south and west of our area, although it is close. Do not plan on issuing any winter weather advisories at this time for CT or RI. However with the cold temperatures overnight, any snow showers that do occur will accumulate on the roadways just in time for the morning commute. Will issue an SPS to highlight this concern for tomorrow morning. Anyone traveling should take it slow as roads can become slick. Overall snow accumulations will be around a coating to less than an inch. Snow should end by the mid-morning hours as the better lift moves northward. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... Monday afternoon into Monday night... ***Low chance for spotty freezing rain across Northeast Massachusetts late Mon Afternoon*** Warm front to the south will begin to push into southern New England during the day on Monday. Despite southerly winds at the surface, 2m Temps from Hi-res guidance suggest that the front will struggle to push through keeping many sites in the low to mid 30s. May see some warming on the south coast to near 40F but it will be a struggle. Any lingering precip from the morning hours will be spotty and very light as the better lift continues to remain north of the region. However profile is still quite saturated so any forcing could help result in some showers. Depending on surface temps this could be snow or rain. Precip chance for the afternoon into the evening will linger across northeast MA as meso-low moving into coastal ME seems to develop some sort of inverted trough over that region. With this lingering moisture combined with increase 950mb warm layer, could see some freezing rain by later afternoon into evening hours. This could result in impacts to the evening commute in northeast MA. This is shown in BUFKIT soundings especially for BVY, LWM and BED. It will be close for BOS. Confidence is to low, and precip could be quite spotty so will hold off on winter weather adv for now. Something the overnight shift may want to look at. Shower chances decreases by the late evening resulting in a dry forecast for Monday night. Temperatures will remain steady as weak warm front pushes northward. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Highlights... * Much milder Tue with mainly dry weather * Turning blustery and colder Wed into Thu with dry weather * Mainly rain Fri night/Sat with some wind and mild temps favored * Unsettled weather possible sometime Christmas Eve into Christmas Details... Tuesday... Much milder weather expected on Tuesday with 850T near 0C and southwest flow ahead of a cold front. High temps should reach into the upper 40s to near 50 with even some lower 50s possible in the coastal plain. Dry weather anticipated with the lack of synoptic scale forcing, but can not rule out a spot shower or two toward evening in western MA. Tuesday night and Wednesday... A cold front crosses the region region Tue night into early Wed with colder/blustery weather to follow. Mainly dry weather anticipated other than perhaps a few brief rain/snow showers across the east slopes of the Berkshires. Increasing wind will keep low temps Tue night mainly in the upper 20s to the lower 30s. High temps on Wed will generally be in the 30s to around 40, but northwest wind gusts of 25 to 40 mph will make it feel colder. Wednesday night and Thursday... Canadian high pressure builds into the region bringing dry but cold weather. Low temps Wed night should mainly be in the teens, but some single digits can not be ruled out in the normally coldest outlying locations. High temps on Thu should mainly be in the 30 to 35 degree range, but with less wind than on Wed. Friday and Saturday... Upper level ridging will be building across the southeast states as a shortwave trough lifts northeast towards the Great Lakes. While it is too early to completely lock in a solution...the given pattern and ensemble guidance strongly favors low pressure passing to our northwest putting us on the mild side of the storm. Timing still uncertain, but most guidance keeps the daytime hours dry with bulk of the rain Friday night and/or Saturday. Now there initially is still Canadian High pressure which slides off to the east, so can not rule out the low risk for a bit of snow/ice at the onset across the interior. Regardless, mainly rain is favored Friday night into Saturday across the entire region. In fact, temps could climb well into the 50s to near 60 for a time along with a period of strong southerly winds. Christmas Eve into Christmas... Very low confidence forecast in this time range. Upper level ridge with abnormally high height fields will be anchored off the southeast coast. Meanwhile, a dome of arctic air and well below normal temperatures will be invading much of the central states. This will place our region in the battle ground between these extreme airmasses. A couple waves of low pressure will likely track along the baroclinic zone and bring the risk for a period or two of precipitation sometime Christmas Eve into Christmas. Timing/ptypes and will depend on exactly where the baroclinic zone aligns. While snow is certainly an option especially at this time range...given strength of southeast upper level ridge would favor rain/ice. If we do have enough cold air for wintry precipitation, it might end up coming down shallow given rather high height fields which could possibly result in more of an ice threat than snow. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/...High confidence. Tonight...VFR with gradually lowering cigs through midnight. Mainly MVFR conditions overspread western MA/northern CT in light snow between 6z and 9z. These conditions may reach eastern MA and RI towards 12z. Monday...Widespread MVFR cigs with a few spots lowering IFR. Chance of light snow north of the Pike and rain south of the Pike. Precip will wind down by the afternoon. Lingering showers in Northeast MA could result in a wintry mix resulting in slick runways. Monday night...Improving conditions to VFR during the overnight. KBOS Terminal...Moderate confidence. Spotty light snow showers may arrive towards 12z and persist at times into the late Monday morning hours. May have to watch for spotty -fzdz after 20z. Low confidence if this will occur. KBDL Terminal...High confidence. Light snow will likely impact the terminal mainly between 6z and 10z Monday morning. Outlook /Tuesday through Friday/... Tuesday: Mainly VFR, with local MVFR possible. Windy with gusts to 30 kt. Tuesday Night: Mainly VFR, with local MVFR possible. Windy with gusts to 35 kt. Wednesday: VFR. Windy with gusts to 35 kt. Wednesday Night through Thursday: VFR. Breezy. Thursday Night: VFR. Friday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday Night/...High confidence. Tonight...Light winds and seas. Monday...Winds becoming SW and increasing in the afternoon but gusts below 20 kt. Seas below SCA. Chance of light snow changing to rain. Monday night...Dry weather with increasing winds and seas. Conditions remain below SCA. Outlook /Tuesday through Friday/... Tuesday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Tuesday Night: Moderate risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Wednesday: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Wednesday Night: Moderate risk for Small Craft Advisory winds with areas of gusts up to 30 kt. Local rough seas. Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Thursday Night: Winds less than 25 kt. Friday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/Dunten NEAR TERM...KJC/Frank/Dunten SHORT TERM...Dunten LONG TERM...Frank AVIATION...Frank/Dunten MARINE...Frank/Dunten
Area Forecast Discussion
National Weather Service Columbia SC
1052 PM EST Sun Dec 17 2017 .SYNOPSIS... High pressure will shift off the Carolina coast overnight. There will be increased moisture in the southerly flow on the backside of the offshore high Monday. Additional rain chances throughout the week expected with a weak front across the area. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... Latest regional radar loop showing precipitation has become quite spotty across the region with mainly only sprinkles out there as the isentropic lift has weakened. Despite the best moisture transport over the area currently, precipitable water values will be lowering through the remainder of the night. Most recent HRRR run showing little additional significant reflectivity returns overnight, just continued isolated sprinkles and possibly a shower or two mainly in the CSRA. Have adjusted hourly grids to account for this and also adjusted temperatures as observations are running a few degrees warmer than forecast. Widespread and increasing clouds should limit radiational cooling this evening and overnight so expecting much warmer min temperatures tonight compared to last night with lows in the mid 40s to low 50s. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... An upper level disturbance falls apart as it moves into the mean ridge axis over the Southeast U.S. A very dry antecedent airmass over the Carolinas will also inhibit chances of precipitation with this disturbance. A second stronger upper level trough is forecast to impact the region starting on Wednesday. A warm front should be located near the North Carolina/South Carolina border with overrunning rain. Temperatures will be well above normal south of the front. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... A strong disturbance moves off the Carolina coast Wednesday Night with overrunning rain coming to an end. High pressure aloft rebuilds Thursday into Friday with dry weather and well above normal temperatures. A cold front is forecast to sweep into the region this weekend with a deep and broad upper trough across much of the U.S. next weekend. The surface front may become parallel to the upper flow and stall somewhere near the region early next week. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... VFR conditions through the early morning hours...then restrictions expected through the end of the period. Clouds have continued thickening and lowering over the past couple of hours with regional radar showings only a few widely scattered showers. With additional moisture moving into the region overnight cigs expected to become MVFR at AGS/DNL around 06z and remaining terminals around 10z. Chance of rain remains too low to include through 15z...then have included VCSH for AGS/DNL/OGB with VCSH for CAE/CUB beginning 18z. For threat overnight remains low...however have included for AGS during the early morning and sunrise hours. Winds through the period will be southwesterly at 5 knots or less. EXTENDED AVIATION OUTLOOK...Boundary will remain stalled across the region with rain and associated restrictions at times through Wednesday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
Area Forecast Discussion
National Weather Service Grand Forks ND
646 PM CST Sun Dec 17 2017 .UPDATE... Issued at 629 PM CST Sun Dec 17 2017 Fog and low stratus deck the main concern and impact this evening and overnight. Lowest visibilities so far at Crookston METAR showing a half mile. Will continue to monitor its evolution and coverage. Dense fog advisory a definite possibility this evening, will see how observations do over the next couple hours. && .SHORT TERM...(This evening through Monday) Issued at 200 PM CST Sun Dec 17 2017 Concerns will be fog potential tonight and then snow chances on Monday. 12z guidance in good agreement. Lots of questions regarding clouds and fog potential for tonight. Clouds and fog remain this afternoon where SFC dewpoint values are in the upper 20s/low 30s. Latest RAP guidance indicates this low level moisture will remain in place, and advect northward this evening, placed along and east of the valley. With this thinking in mind, will go mostly cloudy with fog east of the valley. Not sure about dense fog potential but will monitor into the evening hours. Anticipate high clouds overtaking the region by 12z Mon. Warm air advection overnight will make min temp forecast tricky. Steady temps along with clouds. Areas with no clouds this evening will likely see a quick temperature drop before steadying and possibly slowly rising. How far these temps fall is uncertain. Left exit region of a strong upper level jet brings forcing and snow chances to the northern half of the region on Monday. Increase these snow chances based on the latest guidance. Most guidance also indicating weak MUCAPE (up to 50 J/KG). Given the forcing along with the potential for weak instability, convective type snow showers could lead to a quick 2-4 inches on Monday. Main message is for widespread snowfall totals of 1-2 inches with localized snowfall up to 4 inches possible. .LONG TERM...(Tuesday through Sunday) Issued at 200 PM CST Sun Dec 17 2017 A sfc ridge builds into the area on Tuesday with NW flow aloft becoming more zonal by Wednesday. This will allow an abundance of Pacific moisture to move across the northern Rockies and into the northern tier as sfc low pressure develops lee of the Rockies and moves across the plains. Models continue to show a band of snow across the CWA Wed aftn...for the best chance of widespread snowfall accumulations in the long term period. Models are showing significant snowfall accumulation in the Cascades/Northern Rockies so QPF amounts still in question as well as track of sfc features, but do think one to three inch accumulations across at least eastern ND is possible. QPF amounts and calculated snow fall accumulations did come in a bit lower today which makes sense with what is expected in the PAC NW. Beyond Wed, low chances of snow continuing across the far south into Friday but main feature is a push of cold air that brings Christmas Eve highs possibly into the single digits below zero across the northern two thirds of the CWA. Adjusted temps with a 50/50 Superblend/CONSALL solution for Thu-Sun, however coldest temps will be dependent on cloud cover, winds, and where exactly the freshest snowfall sets up mid week. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 629 PM CST Sun Dec 17 2017 LIFR conditions at TVF trying to work into FAR and BJI this evening as low stratus deck with fog lifts to the north and expands in coverage this evening across NW MN. Stratus deck will persist into the overnight before it slides to the east towards morning. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JK SHORT TERM...TG LONG TERM...Speicher AVIATION...JK
Area Forecast Discussion
National Weather Service Grand Rapids MI
942 PM EST Sun Dec 17 2017 LATEST UPDATE... Update .SYNOPSIS... Issued at 323 PM EST Sun Dec 17 2017 Milder weather can be expected much of this week, especially compared to the last couple of weeks. there is a chance of some precipitation tonight as a frontal system approaches the area. Significant precipitation is not expected, although types could range from rain, to snow, to some freezing drizzle depending on temperatures. The precipitation will clear out by Monday night, and some sunshine and temperatures well into the 40s can be expected. The end of the week will see chances for precipitation increase as a major storm system affects much of the country. This system could bring rain or snow to the area. Behind the system for the upcoming Christmas holiday, colder weather is expected to settle back in with chances for lake effect. && .UPDATE... Issued at 942 PM EST Sun Dec 17 2017 I updated the chance of precipitation to likely over most of our forecast area overnight. As the day shift forecaster wrote, we will have P-type issues as surface temperatures at this hour are still mostly below freezing. Model sounding suggest areas near and south of I-96 will be warm enough for mostly rain but if the air temperature does not get above freezing before the precipitation begins we may see some freezing rain or freezing drizzle. Also as noted by the day shift forecaster, the DGZ will for the most part not be saturated during the precipitation event expect for a short period north of I-96 in the pre-dawn hours. So, while I do now think most areas will see a between 0.01 and 0.05 inches of precipitation between 3 am and 10 am temperatures will be near to above freezing. Typically to get a significant amount of ice air temperatures need to be below 30 degree, below 28 degrees is even better. I do not think anyplace in our CWA will be that cold when liquid precipitation is falling. So I do not believe we need a Weather Advisory for this event. So, why is it going to precipitate early Monday morning? Turns out we have the right entrance region of a northern stream jet core over upper Michigan tonight while a much stronger southern stream jet core passes over I-80 (130kts). There is a PV wave that is associate with an northern stream trough (seen on water vapor loops) heading this way assoicated with all of this. This results in area of enhanced 1000/850 mb moisture transport aimed at I-94 to I-96 between midnight and sunrise. Also there is 30 to 40 knot low level jet associate with the jet entrance region that moves into Southwest Michigan toward sunrise. All of this working together results in enough lift for some light precipitation. It should all be done with by late morning. There is an issue with fog but with all the clouds an precipitation it would seem to me that will not be a big issue overnight. && .SHORT TERM...(This evening through Tuesday night) Issued at 323 PM EST Sun Dec 17 2017 Our main issues in the short term are pcpn trends and type for tonight and into Monday. The good thing is that impacts will be limited to a chance of some light freezing drizzle tonight and Mon morning where temps will be below freezing. Pcpn has tried to make it up north into the area this afternoon, but has not, and will likely not succeed as the deep moisture and wave gets shunted away from the area. We will see better moisture advect in later tonight from the SW, and interact with a weak front coming in from the NW. This will help to develop some pcpn over the heart of the area. Pcpn will be light in nature. P-type issues are present as the atmosphere is initially supportive of snow. The warmer air coming in will try to change pcpn over to some light rain. The sfc temps will drop off a couple of degrees this evening, before coming up gradually overnight. On either side of the best chance of pcpn (roughly from after midnight to daybreak) the DGZ will not be saturated. This will lead to some drizzle/freezing drizzle potential depending on the sfc temp. This should be light and limited in time due to rising temps. We do not think it will be significant enough for any headlines at this time. Fog will become possible also overnight with saturated lower levels. Some light pcpn will linger into the first half of Mon before the front clears out the moisture later in the day. The remainder of the period from Mon night through Tue night looks fairly quiet. There will be a system well north of the area that could bring some flurries into the U.S.-10 corridor on the srn flank. That will move out, and eventually we will see clearing take place for Tue. Temps on Tue with sunshine and nice warm air advection will likely climb well into the 40s. .LONG TERM...(Wednesday through Sunday) Issued at 323 PM EST Sun Dec 17 2017 The main challenge in the long term deals with the impacts from the storm for the end of the week. Models are in reasonable agreement in showing warm air advection will be underway Wednesday night into Thursday. The combination of lift and deepening moisture will result in some snow. Overall the impact potential looks limited as the low levels remain relatively dry. There are some indications that a warm above freezing layer will try to move in aloft on Thursday. If this happens we could see more potential for liquid precipitation. The GFS suggests a deeper further west track to the storm...bringing the warm sector into Southwest Lower MI on Friday. While the High Res Euro tracks the low through the central parts of the CWA and keeps the storm weak. Either way any mixed precipitation Thursday night should change over to all rain. There is some risk for a slick Friday morning commute...that will need to be monitored. I would not rule out some freezing rain as well. If the GFS is right...there could be thunderstorms around Friday. Elevated instability is seen in the model with some suggestion of surfaced based instability as well. The High Res Euro shows much less potential for that to happen. Will not introduce storms at this point...but will need to monitor trends closely in the coming days. As the colder air starts to work in behind the departing storm...will feature falling temperatures. At this point the potential for impactful lake effect looks low for Saturday into Sunday. There are indications that a wave may form along the frontal zone on Sunday which could lead to an increased risk for snow. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 625 PM EST Sun Dec 17 2017 While it is hard to tell from IR satellite loops skies have cleared below 12,000 ft at AZO, BTL, JXN and BIV and should soon do the same at GRR. Maybe even MKG and LAN will clear of the low clouds for a few hours this evening. This is shown well by the HRRR Layered cloud forecast, which by the way is tracking nicely over the past 3 hours. So, I used the HRRR Layered cloud forecast to do the 00z TAFS. The low clouds will fill back in by 06z or so at all TAF sites. There is a wave on the front that comes through the area toward morning. This should bring some light rain or drizzle to our TAF sites. The glitch is temperatures are currently below freezing at MKG and GRR and near freezing at LAN. The other TAF sites are 33 degrees. It would not be out of the question this could be freezing rain. However the hi-res models show winds becoming more southerly than easterly overnight. That will bring up the warmer air from the south into our area mitigating the risk of freezing precipitation. Still it is not out of the question. That should more out of the area prior to noon, then just low clouds and some light fog the rest of the day Monday. && .MARINE... Issued at 323 PM EST Sun Dec 17 2017 We will be issuing a Small Craft Advisory that will be effective Mon afternoon through Tue. This will likely need to be extended out in time eventually, but we do not want to go too long for the time being. Winds pick up after the front/wave move through tonight into Mon morning. A decent gradient sets up, and will likely last into Tue night before diminishing enough. Waves will build up to around 8 feet or so. && .HYDROLOGY... Issued at 323 PM EST Sun Dec 17 2017 A few gauge sites remain ice affected, most notably the Looking Glass at Eagle and the White River at Whitehall. Of the two, Eagle is the only site with a level confirmed to be above bankfull. All sites are stable at this point and the Looking Glass River continues to recede. Improvement is expected to continue with warmer temperatures over the course of the work week. Precipitation is also manageable with only a few tenths of an inch forecast through the next 7 days. Flood risks are minimal. For now, concerns are largely focused on behavior existing ice jams. Otherwise, no addition flooding is expected at this time. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory from 2 PM Monday to 7 PM EST Tuesday for LMZ844>849. && $$ UPDATE...WDM SYNOPSIS...NJJ SHORT TERM...NJJ LONG TERM...MJS AVIATION...WDM HYDROLOGY...JAM MARINE...NJJ
Area Forecast Discussion
National Weather Service Lincoln IL
823 PM CST Sun Dec 17 2017 .UPDATE... Issued at 823 PM CST Sun Dec 17 2017 Some scattered areas of light rain continue across the northern third of Illinois this evening, with short range high-res models suggesting will continue through the night. Further south, it should be more of a patchy drizzle, though this will wait until we start getting a more widespread low stratus overhead. Latest observations showing a large part of the forecast area southeast of the Illinois River and north of I-70 with clouds as high as about 5,000 feet, though this will lower the rest of the evening. Temperatures should hold fairly steady or only fall a couple degrees at best. Updated zones/grids have been sent for the latest trends. && .SHORT TERM...(This evening through Monday) ISSUED AT 310 PM CST Sun Dec 17 2017 Mid afternoon surface analysis shows weak 1015 mb low pressure over south central Iowa with its warm front extending eastward across northern IL, just north of I-88. A few light rain showers lingered north of Lincoln and the latest HRRR models continues isolated light rain showers over northern CWA into this evening. Several large breaks in the clouds over central and eastern IL has allowed temps to elevate into the mid 40s to lower 50s, coolest in southeast IL. Low/stratus clouds over MO along with some fog and drizzle will spread ne across central IL during this evening and linger into Monday morning. Lows tonight only in the upper 30s to around 40F as sw winds 5-10 mph continue. Low clouds to decrease from the west during Monday afternoon though eastern IL likely stays mostly cloudy much of the afternoon. SW winds 8-15 mph to keep temps on the mild side with highs 50-55F, while areas ne of I-74 in the upper 40s. .LONG TERM...(Monday night through Sunday) ISSUED AT 310 PM CST Sun Dec 17 2017 Skies to become mostly clear during Monday night with sw winds prevailing, and lows only 35-40F. Tue still looks like a nice day with partly to mostly sunny skies and highs in the low to mid 50s, even upper 50s sw CWA. A weak cold front pushes through during Tue afternoon and should come through dry with winds shifting nw behind it. Models track a low pressure over southern AR and the southern TN river valley during Tue night keeping its precipitation south of our CWA, though southern areas will see more cloud cover. Lows Tue night in the upper 20s northern CWA and mid 30s along highway 50 in southeast IL. Low pressure tracks toward the Carolina coast by sunset Wed while weak upper level ridging into IL keeping us dry. Cooler highs Wed in the 40s with E/NE winds of 5-10 mph. These temps are still about 10F above normal. Models deepen a strong upper level trof over the Rockies Wed night and Thu and continue trending slower ejecting low pressure into central KS by early Thu afternoon and near the IA/MO border later Thu evening. Thu now looks dry across CWA even nw of the IL river valley with just a slight chance of light rain later Thu evening. Another seasonably mild day Thu in the upper 40s and lower 50s, with some mid 50s southern CWA. Have slight chance of mainly light rain showers overnight Thu night across CWA with a mix possible nw of IL river later Thu night. Lows Thu night range from mid 30s over IL river valley, to lower 40s in southeast IL from I-70 se. Surface low deepens into the western Great Lakes by Fri evening while another low pressure moves into the southern TN river valley by overnight Fri night. This will likely develop precipitation across central and eastern IL during Friday and then diminish from the west during overnight Fri night. Should be warm enough for all rain on Friday, then changing to a mix or snow from nw to se during Fri evening and over southeast IL early overnight Fri night. Could be some light snow accumulations Fri night up to about 1 inch. Highs Fri range from lower 40s nw of IL river to mid 50s by Lawrenceville. Drier and colder air ushers in on Sat on nw winds. Lows Fri night in the low to mid 20s in central IL and upper 20s to around 30F in southeast IL. Highs Sat and Sunday in the upper 20s and lower 30s over IL river valley and upper 30s to near 40F in southeast IL. Extended models have different solutions for next Sunday with active southern stream se of central IL and also a northern stream system moving into the Midwest. Stayed close to consensus for pops next Sunday which has 20-30% chance of snow over the IL river valley. But chances of snow could increase further east across area on Christmas eve/Sunday and Sunday night. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 522 PM CST Sun Dec 17 2017 Currently watching an area of MVFR/IFR ceilings advecting northeast out of Missouri and southern Illinois. Ceilings over the central Illinois TAF sites are around 5-7kft as of 23Z, but will be steadily lowering over the next few hours. Some IFR conditions expected by about 05Z or so, along with some patchy drizzle. While ceilings should start to lift Monday morning, it likely will take until afternoon before rising above 3,000 feet. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SHORT TERM...07 LONG TERM...07 AVIATION...Geelhart
National Weather Service Jackson KY
851 PM EST Sun Dec 17 2017 .UPDATE... Issued at 815 PM EST SUN DEC 17 2017 Hourly pops, sky, temperatures and dewpoints have been updated based on recent observations. Clouds heights are still expected to decrease overnight with subsidence in the wake of the mid level wave that brought precipitation earlier today. Stratus build down to the ridgetop level if not lower should occur overnight. This and weak southwest flow from about 900 mb and below and a weak passing disturbance could still lead to some drizzle. Recent radar images generally just have what appears to be patchy drizzle across the 4 VA border counties and adjacent areas of far southern portions of counties just to the north. Overall, other than some adjustments for recent observation and radar trends, no substantial changes were made at this point. Although drizzle later on tonight is low confidence, confidence in the persistent low clouds and rather mild temperatures is high. Min T will be in the upper 30s and little drop in temperatures overnight from current readings. && .SHORT TERM...(This evening through Monday night) Issued at 345 PM EST SUN DEC 17 2017 20z sfc analysis shows low pressure working into Kentucky with a weakening cold front spreading into our area. This is continuing to support light pcpn and a lowering cloud deck late this afternoon. Under the thick clouds temperatures are holding in the upper 30s to lower 40s most places while dewpoints are in the low to mid 30s. Winds are predominantly light and variable with the higher elevations and locations closer to the Bluegrass seeing southwest ones. They are light to the northwest with stronger ones at 10 to 20 kts above 2000 feet along with some gusts in the 30s. The models are in good agreement aloft through the majority of the short term portion of the forecast, though they diverge a bit late. They all depict fast and nearly zonal flow over the Ohio Valley tonight through Monday night. A dampening wave is currently departing the area with additional energy more concentrated well to the north of Kentucky on Monday. Meanwhile, a fairly deep and closed trough will be swinging through the Four Corners region tomorrow afternoon elongating as it heads into western Texas by Tuesday morning. At this point the models start to stray from each other with the NAM taking the core of the trough further north than the GFS and ECMWF. This difference continues through the day, Tuesday as the ECMWF digs its trough deepest and a bit quicker east than the others. Downstream, this will affect the amount of height rises over Kentucky with additional bits of energy slipping over the JKL CWA. Given the increasing model spread a general blend is preferred, though the higher resolution HRRR and NAM12 were leaned upon for wx details. Sensible weather will feature plenty of clouds through the short term as low level moisture will be tough to clear out. With lowering cigs tonight into Monday drizzle and pockets of light rain can be expected but very little in the way of QPF resulting. In addition the cloud cover will really tamp down the diurnal curve through the entire short term period of the forecast. With the falling cigs some may get low enough tonight for areas of ridgetop fog. Have included this in the grids, as well. Given the limited diurnal range did not deviate too far from the ShortBlend temperatures through the period. Did raise PoPs a notch during most of the short term to help define the drizzle threat. .LONG TERM...(Tuesday through Sunday) Issued at 250 PM EST SUN DEC 17 2017 The latest model data is suggesting that there will be two periods of active weather in the extended. The first will be from Tuesday afternoon through Wednesday evening, as an area of low pressure moves slowly across the Tennessee Valley. Scattered to numerous rain showers are expected for most of the area, as the weather system makes its way off to the east. The second period of active weather looks to be from Friday through early Saturday evening. It appears once again that temperatures will be warm enough to keep any precipitation in liquid form across the area. Both precipitation episodes should provide nothing more than a good soaking rain to eastern Kentucky. Temperatures through out the period are expected to be well above normal, with daily readings topping out in the 50s for most locations. There will be a few days where some spots will only make into the upper 40s, and other days where highs will be in the upper 50s. Nightly lows are forecast fall into the 30s and 40s, which would also be well above normal for this time of year. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) ISSUED AT 735 PM EST SUN DEC 17 2017 After this, lingering low level moisture behind the system that brought precipitation from late Sunday morning into Sunday evening will remain in place through the period. Generally MVFR CIGS and or VIS are reported areawide. VIS is lowest on average in the north and along the highest peaks near the VA border. Weak south to southwesterly flow generally at or below 925 mb tonight should lead to further saturation from the ridges above 2000 feet MSL to the ridgetops further north and west. This and a weak disturbance should also lead to the potential for drizzle and CIGS lowering through the MVFR range and to IFR CIGS for ridgetop airports of KSYM, KSJS, and KJKL as well as LOZ during the 6Z to 15Z period. Ridgetop vis should also decrease during that time with stratus build down fog and it may be dense in some instances. Some improvements into the MVFR range is possible by the last 6 hours of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...GREIF LONG TERM...AR AVIATION...JP
Area Forecast Discussion
National Weather Service Louisville KY
732 PM EST Sun Dec 17 2017 .Forecast Update... Issued at 732 PM EST Sun Dec 17 2017 Patchy drizzle is already occurring across the area so did a quick update to get drizzle in the grids a little earlier than originally planned. No other changes. && .Short Term...(This evening through Monday night) Issued at 230 PM EST Sun Dec 17 2017 As of mid afternoon, regional radar imagery showed an area of showers generally along and east of the I-65 corridor across the lower Ohio Valley. Readings were in the low to mid 40s with overcast skies. The main forecast concern in the short term is drizzle and fog late tonight through Monday and its impact on temperatures. For the remainder of this afternoon, plan on the back edge of the precipitation to quickly move east, giving way to just cloudy skies by late afternoon. As we head into this evening, the low levels of the atmosphere will begin to moisten and saturate from the surface to about 850 mb. Upstream observations show plenty of 500 to 1000 ft ceilings with 3-5 mile visibilities. RAP and HRRR soundings show good signals for drizzle beginning toward midnight. Tonight`s temperatures won`t drop too much with the widespread cloud cover. Plan on lows in the low 40s. Drizzle, fog, and low clouds will start the new work week. We should stay socked in the stratus for most of the day as well. This should keep our highs held down to the low to mid 50s. Some breaks in the clouds are possible late in the day and into Monday night but overall not optimistic that we`ll see much clearing. Lows Monday night will stay in the low to mid 40s. && .Long Term...(Tuesday through Sunday) Issued at 235 PM EST Sun Dec 17 2017 Several weather systems to keep tabs on in the long term period, the first being Wednesday. Confidence in the overall forecast starts above average early on then drops considerably by next weekend and Christmas. An upper level system coming from the southwest US will lift toward the Tennessee Valley by late Tuesday into Wednesday. Rain showers are likely to spread into Tennessee and southern Kentucky late Tuesday then across more parts of central Kentucky Wednesday morning. The trend in the model cycles has been to the north, and the latest model consensus brings in precipitation chances up to the Louisville metro now. However, the highest chances (greater than 50 percent) remain confined closer to the Tennessee border. There`s good agreement that the rain will exit Wednesday afternoon or evening. Plan on highs to be in the upper 40s to middle 50s. Right now, up to 1/2 inch of rain could be possible along the KY/TN border. A deep upper level trough is then forecast to develop across the central US. This will act to bring ridging across the southeast US and warmer temperatures. Thursday`s highs could reach the upper 50s to near 60, with lower 60s possible across southern Kentucky. A strong cold front is then forecast to approach the area late Friday into early Saturday. The 17.12z models generally have the frontal passage late Friday. Showers will become likely ahead of the front during the afternoon or evening hours then a more widespread band of showers will accompany the frontal passage. Soundings show the potential for marginal MUCAPE (100-500 J/kg) developing so couldn`t rule out a few thunderstorms at this time. By early Saturday morning, crashing temperatures behind the front could briefly turn any remaining precipitation over to a mix or wet snow west of I-65. For Christmas Eve and Christmas Day, the forecast confidence drops off. This cycle of models continue to struggle with the strength of a building southeast US ridge. The ECMWF and CMC kept a stronger ridge with a more active, but warmer, zone of weather from the Texas Gulf Coast through the lower Ohio Valley into the Great Lakes. The GFS was a colder, but drier solution. It remains too early to pinpoint details and the best message we have is to continue to closely monitor the forecast this upcoming week for any holiday travel preparations. && .Aviation...(00Z TAF Issuance) Issued at 629 PM EST Sun Dec 17 2017 Sfc-850 RH will remain high through much of the TAF period. Ceilings, already MVFR at the start of the TAF at most locations, will lower tonight to IFR, possibly with some LIFR during the early morning hours especially at BWG and LEX. The low level moisture will remain in place on Monday so low clouds will persist through the day, though there should be enough mixing to push ceilings back up into MVFR. Winds will come in from the southwest at 5 to 10 knots with surface ridging to our east and southeast and a cold front approaching from the northwest by the end of the period. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...13 Short Term...ZT Long Term...ZT Aviation...13
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
830 PM EST Sun Dec 17 2017 .SYNOPSIS... A weak boundary overhead will lift to the north as a warm front tonight into Monday. An upper level disturbance will approach the area from the west Monday afternoon and evening. This disturbance could bring some light precipitation to the Appalachian Front later Monday. High pressure will build in briefly before the next storm system scoots by to our south during the middle of the week. && .NEAR TERM /THROUGH MONDAY/... A warm front was stationed just north of the Potomac River as of 8 PM. Removed mention of sleet along the Mason-Dixon line as dew points have risen to 30+ degrees and air temperatures are in the lower 40s. Wet bulb 0 C heights are, at best, 2500 feet. Otherwise, forecast on track with sprinkles or spotty light rain ending this evening as the warm front lifts north. Skies are expected to remain mostly cloudy overnight. Low temperatures will bottom out near or slightly above freezing outside of the major cities, upper 30s in the downtown areas. As for the upslope areas west of the Allegheny Front, moisture/lift appear too shallow/weak for appreciable snowfall accumulation. Some light rain and drizzle mixed with pellets or snow grains seems most likely, with perhaps a light coating at the highest elevations between midnight and daybreak before temperatures warm. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As a warm front pushes to the north Monday, so do the milder temperatures will highs about 5 degrees warmer than Sunday. A light persistent southwest wind will aid in this milder trend. By Monday afternoon into Monday evening, clouds and precipitation will return with the bulk of any precipitation remaining light and mainly confined to the Appalachian Front in the form of light rain or drizzle. A leeside trough of low pressure should set up just to the east of the Appalachian spine, thus, allowing for this precipitation to occur with the help from a weak mid- level disturbance. Tuesday should be even milder yet with highs ranging from the middle 50s to the middle 60s widespread across the region. A persistent southwest wind and a little added sunshine during the day should aid in this. Tuesday night will be about the same as Monday night with low temperatures dropping into the middle to upper 30s for the most part. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Southern stream shortwave energy will be approaching the Mid-Atlantic region on Wednesday into Wednesday night. Guidance suggests that the forcing will stay south of us, but showers associated to this system could reach the southern counties of our CWA. Still to be determined in more detail is timing and p-types. A ridge of high pressure builds over the region on Thursday and into Thursday night bringing a period of dry weather. Sometime on Friday a warm front will push through, followed by a cold front on Saturday. Models suggest that Friday will remain on the drier side while Friday night we might see showers ahead of the front, but it all depends on the timing of it. Saturday`s PoPs are higher with the front moving through the region from the west. Uncertainty exists on Sunday`s weather depending on how close to the area the front stalls. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... Winds generally southwest less than 5 knots through Monday. VFR conditions expected tonight through Tuesday night. HRRR hinting at some MVFR visibility 9-12Z INVOF IAD/BWI/MTN tonight. Can`t rule out brief patchy fog in these areas if breaks in clouds develop given high RH values/calm winds. Some guidance (namely the MET) is hinting at fog development near the Bay Monday night which makes sense given light winds and environmental dew points higher than water temperatures. Mainly VFR conditions expected the second half of the week. && .MARINE... No marine hazards through Monday night. Winds become light and variable tonight, then southwest 5-10 kts Monday into Tuesday. Fog is possible over the waters Monday night which makes sense given light winds and environmental dew points (mid to upper 40s) higher than water temperatures (around 40). Winds should increase late Tuesday into Wednesday near and behind a cold front. Small Craft Advisories may be needed for portions of the waters during this time. Near shore waters likely see gusts first since open waters will be much cooler than environmental airmass. Mixing would presumably be more difficult over open waters until a cooler airmass arrives later Tuesday night into Wednesday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...KLW NEAR TERM...KLW/DHOF SHORT TERM...KLW LONG TERM...IMR AVIATION...IMR/KLW/DHOF MARINE...IMR/KLW/DHOF
Area Forecast Discussion
National Weather Service Midland/Odessa TX
518 PM CST Sun Dec 17 2017 .DISCUSSION... The latest Aviation Discussion is included below. && .AVIATION... VFR conditions will prevail most of the night at all area terminals. However, fog may form late, if not an IFR ceiling, and have included these lower conditions at all but KCNM and KFST. Since there is some uncertainty on timing and extent, have only put temporary IFR ceilings and MVFR visibility at the rest of the terminals. If an extensive low cloud deck forms, sites may be affect through 18/17Z. && .PREV DISCUSSION... /issued 226 PM CST Sun Dec 17 2017/ As of 2:00 PM CST Sunday...For the Christmas weekend the only thing consistent is the inconsistency of the medium range models. At least for this 12Z suite of models the GFS...ECMWF...and Canadian are not consistent with themselves let alone with each other. We`ll see where this game of musical models stops over the next several days. In the short-term the HRRR and RAP13 are indc ample low level moisture moving into portions of the area.Therefore have put in patchy fog (temps should remain above freezing so no freezing fog is expected) for the central and eastern portions of the CWA late tonight into Monday morning. The upper low over extreme southwest Arizona will weaken as it lifts northeast into the TX Panhandle on Tuesday. Have pulled back pops and have just kept them in for the extreme western portions of the CWA...temps will be warm enough for all rain. Have kept pops in the southeast CWA on Tuesday with the deeper moisture. In general...all the medium range models keep the CWA dry with above normal temps thru Thursday (normal for MAF is 57). As mentioned above the models are not consistent for the holiday weekend...with the GFS and ECMWF now significantly warmer and the Canadian much colder. Due to this inconsistency have not made any changes to the extended forecast...since we want to avoid making big changes (at least to we see some consistency). Strobin && .PRELIMINARY POINT TEMPS/POPS... Big Spring 38 59 43 62 / 0 10 10 10 Carlsbad 38 60 40 62 / 10 10 10 0 Dryden 42 64 47 69 / 0 0 20 10 Fort Stockton 40 63 44 64 / 0 0 10 10 Guadalupe Pass 41 53 37 52 / 20 10 10 0 Hobbs 36 58 38 60 / 0 0 10 10 Marfa 35 62 36 58 / 0 0 10 10 Midland Intl Airport 38 60 40 62 / 0 10 10 10 Odessa 38 60 40 62 / 0 0 10 10 Wink 38 60 40 63 / 0 0 10 10 && .MAF WATCHES/WARNINGS/ADVISORIES... NM...None. TX...None. && $$ 49/33
Area Forecast Discussion
National Weather Service Marquette MI
535 PM EST Sun Dec 17 2017 .SHORT TERM...(This evening through Monday) Issued at 356 PM EST SUN DEC 17 2017 WV imagery and RAP analysis indicated mainly zonal flow through the nrn CONUS and srn Canada with a shortwave trough over nrn Ontario near CYPL. At the surface, weak srly flow prevailed as high pres moves to nrn New England and low pressure develops over the plains. Radars indicated weak returns from nw Wi into Upper Michigan with sfc reports showing some light snow over far nrn WI. Tonight, expect the light snow, supported by 800-600 fgen to slide through the cntrl and ern cwa this evening. However, with only weak to moderate forcing and little moisture inflow, only lower end POPs were included with little or no accumulation expected. Any lingering light snow should end by around 06z. Monday, southwest winds will increase as a deep low moves through cntrl Canada to far nw Ontario. WAA will help push temps above seasonal averages with highs in the lower to mid 30s. A shortwave moving toward nrn MN, with upper level div in the left exit of the 250-300 jet, may help to spread some light snow into wrn Lake Superior and possibly into the far wrn cwa late. .LONG TERM...(Monday night through Sunday) Issued at 347 PM EST SUN DEC 17 2017 Monday night through Wednesday: A series of embedded trough axes rounding a broad mid-level low over Hudson Bay will brush the CWA the during this time. A strong surface pressure gradient juxtapose with a favorable isallobaric wind will promote gusty W/WNW winds late Monday night into Tuesday evening. 925-850hPA winds of 40-45kts should allow for surface gusts to 40mph across the Keweenaw Peninsula late Monday night through much of Tuesday. Though 850hPa temps of just -10 to -12C and reduced residence time from the stronger winds will limit LES intensity, intermittent white out conditions will be possible given the added component of blowing snow from the current snowpack. This concern will also translate to the immediate shore of Lake Superior from Munising eastward Tuesday evening. As noted, LES should be limited early on Tuesday, but a secondary trough axis will bring more favorable thermodynamic conditions for LES Tuesday evening. A period of moderate LES will be possible for the W to NW wind snow belts Tuesday night into Wednesday before lowering inversion heights subdue the LES into Wednesday evening. Wednesday night through Sunday: As can be expected this time of year, model guidance continues to show decent run-to-run differences with the evolution of the large scale pattern and associated period of active weather across the western Great Lakes. The main message is that high-impact weather may affect early holiday travel somewhere across the region during this time. Light WAA snow should spread across the CWA late Wednesday evening into Thursday morning, producing sub-advisory accumulations across the SW half of Upper Michigan. Guidance begins to diverge after this as notable disagreement develops with the handling of lee cyclogenesis in the central and southern Plains as a mid-level trough ejects from the four corners region. Contrary to yesterday, the GFS has become the strongest and northern most solution with this low, bringing a period of high-impact snowfall to Upper MI late Thursday morning into Friday night. The ECMWF and CMC model bring a broader swath of moderate snow across Upper MI Thursday evening into Friday, keeping more significant precipitation well south of the region. Again, given the highly varying solutions, providing any detailed forecast is nearly impossible at this point. However, those who could be affected by moderate to heavy snow accumulations in the western Great Lakes Wednesday night into Saturday should continue to monitor forecast updates through the upcoming week. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 535 PM EST SUN DEC 17 2017 There is enough low level moisture upstream that conditions will continue to be in the IFR/LIFR range for the most part tonight. More substantial dry advection with improving conditions is expected Monday afternoon with improving conditions. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 356 PM EST SUN DEC 17 2017 Southwesterly winds will increase to 20 to 30 knots Monday over the west and north central portions of Lake Superior possibly reaching gales late Mon afternoon and evening before veering to northwesterly gales to 35-40 knots late Mon night into Tue night. With increasing wave heights and colder air temperatures, freezing spray is possible Tuesday night into Wednesday. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... Gale Watch from late Monday night through late Tuesday night for LSZ243>245-264>267. Gale Watch from Tuesday morning through Tuesday evening for LSZ162-241-242-246-247-263. Gale Watch from Tuesday morning through late Tuesday night for LSZ248>251. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...Kluber AVIATION...07 MARINE...JLB
Area Forecast Discussion
National Weather Service Norman OK
859 PM CST Sun Dec 17 2017 ...Update... && .DISCUSSION... Based on trends we have issued a Dense Fog Advisory for portions of central and southern Oklahoma. Despite cirrus, we can faintly see back edge of low stratus working northeast across south-central Oklahoma in IR shortwave imagery. As this occurs, radiative cooling will increase enough for fog formation given how moist the low levels remain. Cirrus may temper radiative cooling some, but not enough to prevent several locations from falling to around or possibly below one quarter mile later tonight. Further east where low stratus remains, low level saturation has been deep enough for persistent light drizzle in/around Shawnee and Chandler to near Ada. This should gradually diminish as depth of saturation decreases per RAP and HRRR forecast soundings. Once this happens, and especially when/if low clouds clear, dense fog may occur across these areas and we will probably need to expand the advisory eastward. Across southwest Oklahoma, light winds and at least modest radiative cooling beneath cirrus will probably eventually result in fog, but we kept the advisory out of these counties for now given the fairly large T/Td spread. We may need to expand west to include a few more counties later tonight. Otherwise the forecast remains on track. Earlier we lowered temperatures considerably across the northwest where cirrus is not present and good radiative cooling is expected. Minor/insignificant adjustments were made elsewhere to various weather elements. BRB && .PREV DISCUSSION... /issued 517 PM CST Sun Dec 17 2017/ AVIATION... Area of low clouds will gradualy clear across western sites, but expect that after sunset that this dissipation of the clouds will slow or stop through much of the night. Therefore will keep a MVFR ceiling at OKC/OUN/PNC through the night with some patchy fog late. Will also mention the possibility of some fog at most sites overnight, but with lack of moisture west and cloud cover east, will keep visibility at 1 mile or higher. Will have to monitor closely however. Expect VFR conditions to overspread the area by mid-morning with some afternoon high clouds streaming in from the southwest. Winds will remain light. PREV DISCUSSION... /issued 355 PM CST Sun Dec 17 2017/ DISCUSSION... For tonight, fog will be the primary issue. Dew points are currently in the low to mid-40Fs across the eastern two-thirds of Oklahoma and adjacent parts of north Texas. As skies clear from the west, temperatures are expected to cool info the mid-30Fs to 40Fs in this area. With a such a large difference in dew points and forecast low temperatures, fog (potentially dense) is expected to develop later tonight across the eastern two-thirds of the area. By Tuesday, a closed-low is forecast to lift northeastward into the Southern Plains. Rain is likely across southeast Oklahoma as this system passes by the area. Some thunder is still possible as well with some elevated instability. Rain chances decrease with north and west extent. Dry and above-average temperatures are expected in the system`s wake for Wednesday. For the frontal timing on Thursday, both the 17/12Z GFS and ECMWF have slowed the cold front down due to a slower passage of the attendant shortwave trough. Therefore, another warm day is expected for Thursday with the cold front entering northwest Oklahoma late afternoon. The slower timing may allow greater moisture advection ahead of the front, which may result in a better chance of rain across eastern Oklahoma Thursday night. The air mass behind the initial cold front may not be as cold as previously forecast with the primary longwave trough remaining to the west as the initial shortwave lifts northeastward. Therefore, forecast high temperatures are slightly warmer for Friday and Saturday afternoons. By Sunday, there continues to be disagreement between the GFS and ECMWF. The previous runs of each model don`t even agree with each other. Even within the GEFS (GFS Ensemble Forecast System), there is high variance among the 20 members--so overall predictability continues to be very low in this period. At this time, the ECMWF and Canadian models are in closest agreement with a high-amplitude ridge off the east coast and a high-amplitude trough across the western United States. This places the Southern Plains within a baroclinic zone/faster flow aloft. A secondary surge of colder air may advect southward on Sunday as well. Will maintain a low chance of snow for Sunday, primarily across northwest Oklahoma, as embedded waves within the southwest flow could result in snow. With the continued uncertainty, the bottom line is exactly the same as yesterday: Colder weather is expected late this week with at least a low chance of winter precipitation next weekend--but specifics are yet to be determined. There are some indications that even colder weather will be possible beyond this forecast period as another surge of cold air moves southward. Mahale && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 47 38 59 45 / 10 0 0 10 Hobart OK 49 35 55 41 / 0 0 10 10 Wichita Falls TX 54 38 56 47 / 0 0 10 10 Gage OK 48 25 60 37 / 0 0 0 0 Ponca City OK 49 38 56 41 / 10 0 0 0 Durant OK 50 43 56 50 / 10 10 10 20 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...Dense Fog Advisory until 9 AM CST Monday for OKZ018-019-023>031- 038>042-045>047-050-051. TX...None. && $$ 12/30
Area Forecast Discussion
National Weather Service Tucson AZ
135 PM MST Sun Dec 17 2017 .SYNOPSIS...Valley rain and mountain snow showers associated with slow moving low pressure south of Arizona will gradually dissipate tonight as the low moves east. Wraparound moisture will allow for some lingering mountain snow showers east of Tucson on Monday, but drier air will move into the area through mid week. A trough will sweep through the Four Corners late in the week bringing increased cloud cover and cooler temperatures, but at this time it doesn`t look to bring much in the way of precipitation. Cooler temperatures will linger through next weekend. && .DISCUSSION... Scattered rain and snow showers continue across the area this afternoon, although areal coverage is substantially less than what was seen earlier this morning. Upper low has moved little today although water vapor imagery clearly shows that a lobe of shortwave energy has already moved through southeast Arizona and is pushing eastward into New Mexico. Regional radar imagery is showing another round of precip forming south of Tucson as of 20Z and this fits well with the past few runs of the HRRR. After 00Z the HRRR isn`t very enthused with precip chances for the rest of the night, only depicting widely scattered showers across the area. I`ll leave the Winter Wx Advisory in place as is to account for the precip that`s about to move through the area as it`ll easily produce a few inches of snow above 6000ft. If things quiet down after sunset the Advisory can always be cancelled a few hours early. Precip chances don`t go away completely as the upper low and its associated moisture will slowly shift into New Mexico on Monday. Wraparound moisture could result in scattered valley rain/mountain snow showers along the AZ/NM border tomorrow although any snow accumulations would be light and it doesn`t appear they`d be enough to warrant the extension of the aforementioned Advisory. The low will finally exit the area Monday night with drier air moving into the area. Dry weather with below normal temps will prevail through mid week. The potential for a mid/late week storm still exists, but today`s deterministic 12Z runs keep the storm track well north of the area and only depict an increase in clouds and wind coincident with the passage of the trough. GEFS plumes aren`t enthused about precip chances either, same story with the EC ensemble mean QPF (a few hundredths of an inch in the White Mtns, that`s about it). Very low (single digit) precip chances later this week look to be all that are warranted at this point. The trough will usher in much cooler air to the area with widespread freezing or near freezing temps possible to close out the week into the weekend. If the current forecast verifies we may need to look at freeze warnings for the deserts before all is said and done. Looking forward to Saturday/Sunday - differences remain between the GFS/EC deterministic guidance with respect to how a trough evolves as it moves through the Pac NW into the northern Great Plains and if/how another trough develops offshore. GFS and associated ensembles suggest Arizona sees the influence of the offshore low with warmer temperatures across the region. EC and ensembles depict a much cooler system with Canadian cold air moving into the area. Neither solution depict precipitation across southeast Arizona but temperatures are up for debate. Will stick with a colder than normal solution for now per the NBM. && .AVIATION...Valid thru 19/00Z. Cloud decks generally around 2-5k ft AGL with layers above thru about 18/05Z, then increasing to 4-7k ft AGL from Tucson westward with gradual clearing overnight. Areas east of KTUS will remain BKN- OVC at 3-6k ft AGL into Monday. SCT valley SHRA and mountain SHSN will continue into this evening, then gradually taper off overnight. Some lingering valley SHRA and mountains SHSN is possible Monday east of Tucson. MVFR cigs/vsbys will occasionally accompany the SHRA especially near terrain and east of Tucson into this evening. Winds mainly southeasterly at around 8 to 12 kts, though occasional gusts to 25 kts may occur in/near stronger SHRA this afternoon, then mainly less variable at 10 kts or less through Monday. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Low pressure will bring much higher relative humidity and scattered precipitation to the area through Monday. East to Southeast winds this afternoon will give way to relatively light/diurnally driven winds during through midweek. Once the current weather system moves to the east, expect dry weather the remainder of the week. As a weather system approaches Thursday, expect some increased breezes. The bulk of this system will pass to our north, thus dry and cool weather to end the work week and into next weekend. && .TWC WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 11 PM MST this evening for AZZ510>514. && $$ Leins/GL Visit us on Facebook...Twitter...YouTube...and at